The invention relates to a method for cleaning a print head of an ink jet printer by a cleaning tape, and to a device for cleaning a print head of an ink jet printer, including a cleaning tape and a suction device.
During relatively long printing pauses, thickening of the ink in the interior of the nozzles of an ink jet print head is possible and can result in disruptions when the printing operation is resumed. In order to prevent this from occurring, the nozzles are usually sprayed clear, as is also the case in an arrangement described in the published European Patent Document EP 0 389 481 B1. This heretofore known arrangement comprises a cleaning device with an endless tape and an ink droplet sensor with a suction block. The endless tape may be formed of rubber or an elastomer, and the suction block acts as a type of suction pump with a capillary effect. No provision has been made for removing ink nor is it technically possible to remove ink from the print head by using the suction block, which serves a quite different purpose. Spraying the nozzles clear requires the application of a positive pressure thereto, due to which small air bubbles which are caught in the corners within the nozzles are compressed in a detrimental manner and pressed still further into the corners, and are thus not released from the corners, which can lead to printing disruptions.
U.S. Pat. No. 5,730,538, and the published German Patent Documents DE 40 00 454 C2 and DE 197 04 003 A1 further describe the state of the prior art.
It is accordingly an object of the invention to provide a method for cleaning a print head by which printing disruptions are avoided, and to provide a device for performing the method effectively.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for cleaning a print head of an ink jet printer by a cleaning tape, which comprises sucking away printing ink from the print head by a suction device, and wiping or doctoring off the print head by the cleaning tape.
In accordance with another mode, the method of the invention includes simultaneously performing the sucking away of the printing ink from the print head, and the wiping or doctoring off of the print head.
In accordance with a further aspect of the invention, there is provided a method for cleaning a print head of an ink jet printer by a cleaning tape, which comprises sucking printing ink from the print head by a suction device onto the cleaning tape.
In accordance with an added mode, the method of the invention includes sucking the printing ink by the suction device out of the interior of at least one nozzle formed in the print head.
In accordance with an additional mode, the method includes sucking the printing ink by the suction device out of the interior of at least one nozzle formed in the print head.
In accordance with another aspect of the invention, there is provided a device for cleaning a print head of an ink jet printer, comprising a cleaning tape and a suction device, the cleaning tape being disposed between the print head and the suction device.
In accordance with a further feature of the invention, the cleaning tape rests both on the print head and on the suction device.
In accordance with an added feature of the invention, the cleaning tape is formed of air-permeable material.
In accordance with an additional feature of the invention, the cleaning tape is formed of absorbent material.
In accordance with an additional aspect of the invention, there is provided an ink jet printer in combination with a cleaning device having at least one of the foregoing features.
In accordance with yet another aspect of the invention, there is provided an ink jet printer, comprising a printing module and a cleaning module, the modules being of compatible construction, so that the cleaning module is optionally combinable with the printing module.
In accordance with yet a further aspect of the invention, there is provided an offset and/or rotary printing machine having integrated therein the ink jet printer with the foregoing features.
In accordance with a concomitant aspect of the invention, there is provided an offset and/or rotary printing machine coupled, for in-line operation, with the ink jet printer having the foregoing features.
The term xe2x80x9cprinting inkxe2x80x9d used in connection with the invention includes both water-based inks and inks of a different composition, for example radiation-curing inks, so-called UV inks, which can be printed by the ink jet printer.
By the method according to the invention, very rapid cleaning of the print head is possible, during which the latter is cleaned mechanically with pneumatic assistance, and the printing ink can be removed from the nozzles by sucking out the printing ink from the print head according to the invention by the suction device, without spraying the nozzles clear.
In a mode of the method that is advantageous with regard to removing printing ink from a nozzle orifice and, simultaneously therewith, the cleaning of a nozzle outlet surface of the print head, the nozzle outlet surface is wiped off or doctored off by the cleaning tape while printing ink is being removed from the print head by the suction device.
In another mode of the method that is advantageous with regard to rapid storage in the cleaning tape of the printing ink removed from the print head, the ink is transferred from the print head to the cleaning tape by the suction device with the assistance of suction air.
In a further mode of the method that is advantageous with regard to the removal of air inclusions from the interior of the nozzle, the printing ink, together with the air included in the nozzle orifice, is sucked out of the nozzle orifice. Printing disruptions which are caused by small air bubbles in the interior of the nozzle and which manifest themselves by the absence of droplet ejection, are thus effectively prevented.
With the device according to the invention, the use of which is not exclusively restricted to the performance of the method according to the invention, the print head can be doctored off or wiped off, i.e., squeegeed, very thoroughly, specifically with pneumatic assistance for the transfer of ink from the print head to the cleaning tape.
In an embodiment of the cleaning device according to the invention that is advantageous with regard to hermetically sealing the area around a nozzle of the print head to which suction is to be applied by the suction device, the cleaning tape rests both on a nozzle outlet surface of the print head, wherein the nozzle terminates or opens, and also over the entire area of the suction device.
In an embodiment of the cleaning device that is advantageous with regard to sucking through the cleaning tape from the rear side thereof, as a result of which the printing ink is sucked onto the front side of the cleaning tape, the cleaning tape is permeable to air.
In an embodiment of the cleaning device that is advantageous with regard to the drip-free storage in the cleaning tape of the soiled or contaminated printing ink to be disposed of, the cleaning tape is formed of a textile or felt-like material.
The cleaning device according to the invention can be assembled from time to time with the ink jet printer for cleaning the print head of the latter. This is advantageous if the print head to be cleaned is comparatively heavy and consequently cannot be displaced or can be displaced only slightly in the horizontal plane for adjustment purposes.
The easily transportable cleaning module of the ink jet printer, which can be assembled and is of modular construction, is preferably constructed to correspond with the device according to the invention and can also be a cleaning device having a construction that differs therefrom and that is designed in an appropriately compatible manner that it can be assembled with the rest of the ink jet printer for the purpose of cleaning the print head.
The ink jet printer is preferably assigned to an offset printing machine, which can be a rotary printing machine, or to a rotary printing machine, which can be an offset printing machine, for combined operation as the impression or numbering unit thereof. With the printing machine, sheet printing material already printed in many colors can thus advantageously be additionally printed by the ink jet printer with individualized codes, for example changing bar codes, consecutive numbers or different recipient addresses.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for cleaning a print head of an ink jet printer, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the figures of the drawings, wherein: